Recently, various types of personal electronic terminals have been popularized. Such personal electronic terminals are provided with functions of performing the transmission and reception of a user's e-mails and other messages, schedule and address directory management and the storage and management of various files that require security in terms of business. Furthermore, personal electronic terminals have excellent portability, and thus it is essential to identify genuine users and to allow the use thereof only to authenticated users.
A password input-type authentication method that is provided by personal electronic terminals in order to perform authentication is problematic in that a probability of exposing a password to another person located adjacent to a user is very strong. In particular, although there is the case where characters that a user inputs are directly exposed to another person, the case in which another person easily infers a password from the locations and input pattern of individual characters frequently occurs. Furthermore, since a password input method that is intended to overcome the above problems should maximize security and take into consideration the convenience of user input, an appropriate alternative has not been proposed for a long period of time.